PEL: Add service procedure to find SUE root cause

An SUE indicates a UE has occurred in another area of hardware. This
procedure instructs service to look for previous PEL for the root cause
of the SUE attention.

Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
Change-Id: Id9b7e6c65a06e52587ac40464456be42b9a557b1
diff --git a/extensions/openpower-pels/registry/schema/schema.json b/extensions/openpower-pels/registry/schema/schema.json
index 7c03f88..7679107 100644
--- a/extensions/openpower-pels/registry/schema/schema.json
+++ b/extensions/openpower-pels/registry/schema/schema.json
@@ -467,7 +467,7 @@
         {
             "description": "The maintenance procedure callout.",
             "type": "string",
-            "enum": ["bmc_code", "next_level_support", "sbe_code", "fsi_path", "power_overcurrent"]
+            "enum": ["bmc_code", "next_level_support", "sbe_code", "fsi_path", "power_overcurrent", "find_sue_root_cause"]
         },
 
         "useInventoryLocCode":